Atypical myopathy is a severe form of rhabdomyolysis that occurs in grazing horses. Over the past decades, the disease has been emerging in Europe. The disease is widespread in Europe and has been suspected in Denmark since 2000, yet no cases have been confirmed. The objective of this study was to confirm cases in this country and to use a new diagnostic technique (aTRAQ assay). Seven out of 8 samples from clinically highly suspicious cases were positive for hypoglycin A, and all had multiple acyl-CoA dehydrogenase deficiency, which confirms that the disease is also present in Denmark. Hypoglycin A levels were lower and clinical signs and mortality less severe than reported in other countries.